What does my boiler error code mean? (and how to fix it)
Boilers can sometimes hit us with confusing error codes, and each one points to a different issue. Here’s a breakdown of some of the most common boiler error codes—categorised by letters—and what they mean, so you can get a better understanding of what’s going on with your boiler.
F-Codes: Common Boiler Errors
- F28 – Ignition failure
Common with Vaillant boilers, this code means the boiler is having trouble igniting. This could be due to a lack of gas, a faulty gas valve, or air in the gas line.
What to do:
Check your gas supply or try resetting the boiler. If it doesn’t fire up, call in a Gas Safe engineer.
- F75 – No pressure change detected
If your Vaillant boiler shows this code, it means the boiler isn’t detecting a pressure change when it fires up. The likely culprits are the pump or pressure sensor.
What to do:
You’ll need an engineer to check both the sensor and the pump to ensure proper functionality.
- F1 – Low Water Pressure
This one’s common on Ideal boilers and indicates that your system’s water pressure has dropped too low for the boiler to function.
What to do:
Top up the pressure using the filling loop. Aim for a level between 1.0 and 1.5 bar on the pressure gauge.
- F22 – Low Water Pressure
Seen in Vaillant boilers, this code means the system is detecting low water pressure, which can prevent the boiler from operating properly.
What to do:
You can re-pressurise the boiler using the filling loop, or call a professional if you’re unsure how to do this.
E-Codes: Common Boiler Errors
- E119 – Low Water Pressure
Found on Baxi boilers, this code indicates low water pressure, which means the boiler can’t function until the pressure is corrected.
What to do:
You’ll need to top up the boiler’s pressure manually. Check the pressure gauge and use the filling loop if necessary.
- E133 – Gas Supply or Flame Failure
On Ideal boilers, this error occurs when there’s an issue with the gas supply or ignition, preventing the boiler from detecting a flame.
What to do:
First, make sure your gas is on and check other appliances. Try resetting the boiler, but if the issue persists, call a Gas Safe engineer.
- E1 – Overheating
Seen on Worcester Bosch boilers, an E1 error usually indicates that the boiler is overheating, potentially caused by a faulty or blocked heat exchanger.
What to do:
Turn off the boiler and call an engineer as soon as possible. Overheating can lead to more serious damage if not addressed.
- E160 – Fan Fault
Often found on Baxi boilers, this code means there’s an issue with the fan that helps vent gases from the boiler. If the fan stops working, the boiler will shut down.
What to do:
This is not a DIY fix—call an engineer to repair or replace the fan.
A-Codes: Common Boiler Errors
- A1 – Dry Fire
This code, commonly seen on Worcester Bosch boilers, indicates the system is detecting no water in the boiler. Without water, the boiler can’t function, and it risks overheating.
What to do:
First, check the pressure gauge. If the pressure is low, top it up. If the issue persists, there may be an airlock or blockage requiring professional attention.
- A7 – Flow Sensor Issue
This code on some boilers, including Vaillant models, means the system has detected a fault with the flow sensor, which is responsible for monitoring water movement in the system.
What to do:
This isn’t something you can fix yourself. Call a heating engineer to replace or repair the faulty sensor.
- A9 – Hot Water Flow Rate Issue
This code can be seen on Worcester Bosch boilers when there’s an issue with the flow of hot water. This could indicate a problem with the hot water temperature sensor or flow.
What to do:
This is a job for a professional, as it may require replacing the sensor.
L-Codes: Common Boiler Errors
- L2 – Flame Loss
This code is common on Ideal boilers and means the boiler has lost its flame, often due to a gas supply issue or ignition fault.
What to do:
Try resetting the boiler. If the flame loss persists, it’s best to contact a Gas Safe engineer.
- L1 – Overheat Lockout
This is another error on Ideal boilers and means that the boiler has locked out due to overheating. This could be caused by a pump issue, airlocks, or a blocked heat exchanger.
What to do:
Turn off the boiler and call a heating engineer to investigate and fix the cause of overheating.
- L5 – False Flame Lockout
This error can occur on Ideal boilers when the system detects a flame even when there’s none. This is usually due to a faulty sensor or issue with the gas valve.
What to do:
This needs professional attention. An engineer can replace the sensor or gas valve to resolve the issue.
When to call in the pros...
Most boiler error codes give you a pretty good idea of what’s going on with your system, but tackling boiler issues isn’t always a DIY job. If you’re unsure or don’t feel comfortable, it’s always better to call a Gas Safe registered engineer to handle the problem safely and effectively.
At Wilsons, we’re experts in diagnosing and fixing boiler issues, from low pressure to more complex mechanical faults. If your boiler is showing an error code and you’re not sure what to do next, get in touch with us! We’ll make sure your boiler is up and running in no time, keeping your home warm and cosy.
